"Hachijo-jima, in the central Izu Islands about 300 km south of Tokyo, consists of two small Quaternary dominantly basaltic stratovolcanoes forming an elongated NW-SE-trending island. The eroded Pleistocene-to-Holocene Higashi-yama volcano occupies the SE end of the 14-km-long island, and the symmetrical Holocene Nishi-yama volcano the NW end. Parasitic cones occur on the SE flank of Nishi-yama. The small volcanic island of Ko-jima lies several km to the west of Hachijo-jima. Growth of Higashi-yama began several tens of thousands of years ago, and included the formation of two small calderas. The initial submarine and early subaerial eruptions of Nishi-yama took place from 10,000 to 8000 years before present (BP). Its latest major activity, from the early Holocene until about 4000 years BP, was restricted to flank eruptions. Historical eruptions of Hachijo-jima, recorded since the 15th century, have been restricted to the summit of Nishi-yama and a submarine vent of unknown location." -Smithsonian Volcano Archive